1. Technical Field
The present invention relates to an optical filter and an analytical instrument.
2. Related Art
In the past, as an optical filter for selecting a light beam having a target wavelength from the incident light beams and then emitting the light beam, there has been known an optical filter of an air-gap type and of an electrostatic-drive type, in which a pair of substrates are disposed so as to be opposed to each other, each of the surfaces of the substrates opposed to each other is provided with a mirror, electrodes are respectively disposed in the peripheries of the mirrors, a diaphragm section is disposed in the periphery of one of the mirrors, and the diaphragm section is displaced due to electrostatic force generated between the electrodes to thereby vary the gap (air gap) between the mirrors, thus taking out the light beam having a desired wavelength (e.g., JP-A-2003-57438).
In such an optical filter, it is required to control a gap between the pair of mirrors in an extremely narrow range such as a sub-micron range through a range of several microns in the manufacturing process, and moreover, it is important to keep the gap between the mirrors with accuracy, and at the same time, to control the gap to have a desired gap amount.
Incidentally, in the optical filter of the air-gap type and of the electrostatic-drive type, the diaphragm is moved by electrostatic attractive force to thereby vary the gap between the mirrors. Therefore, it results that the applied voltage for generating the electrostatic attractive force necessary for the displacement of the gap varies in accordance with the thickness of the diaphragm section. Therefore, it is desirable for the diaphragm section to be as thin as possible in order for holding down the applied voltage. However, thinning the diaphragm section causes degradation of strength, and in the optical filter repeatedly varying the gap stress is applied to the diaphragm section every time the gap is varied, and therefore, there arises a problem that the degradation of strength directly causes breakage of the diaphragm section.